Zusammenfassung der Ressource
Networks And
Communication Part D
- Bandwidth
- This is the measure of how
much data can be
transferred in a time
- The higher the bandwidth
the more data that can be
transferred
- Often measured in Mbps which is bits
per second or Mpbs which is bytes per
second
- The more frequencies
available on a channel
the faster it is
- Bottleneck
- A bottleneck is the smallest bandwidth that
exists between the user and the place that
data is being downloaded from
- The data even though it may have been travelling more
quickly before will get slowed down at the bottle neck
- Cables
- Copper Cable
- Modern copper cables are in twisted pairs, this is
narrow wire that is insulated and twisted in twos,
without an earth wire- known as a UTP or Ethernet
cables, this can sometimes result in loss of data.
- There are also STP cables, these do have
an earth which is a metal shield that
reduces electromagnetic interference,
these have a higher bandwidth capability
so are used in high speed networks
- Coaxial cables which were used in older networks and is still
used in the television industry as it has a capacity for high
bandwidth. This has two wires and the outer cable acts as a
shield to electromagnetic interference.
- Optical Cable
- Fibre-optic cables use small
glass tubes to reflect light
along the tube
- These have much higher bandwidth
as they do not have any electrical
interference
- Wireless
- These can be radio, satellite and infra-red.
- This has a lower bandwidth than the wired methods
- Can be interrupted by physical
obstacles such as walls
- Importance of
bandwidth
- The importance of bandwidth
depends on what it is being used
for
- If something is being streamed then a large
bandwidth is needed
- If something is being downloaded overnight then it
does not matter too much as it is going to be used
the next morning or day
- Live/real time data needs a high
bandwidth as if it does not then it will
freeze and not work well